Dylan Thomas' entry is narrative not verse. Given lyric kinship of song and poetry, carols and hymns are the "canon" (whatever that is). Yet let's not dismiss either carols or popular Christmas poems. Diss them not: they are (along with Mother Goose and Purple Cow) our first exposure to poetry. Even the lofty sonnet began as popular song, possibly sung by women to work by.

Serious (whatever that is) Christmas poetry is thin on the ground. The older it would seem, the better - 17th c puts contemporary to shame. So much for the illusion of progress.

The True Christmas

Henry Vaughan (1678)

So stick up ivy and the bays, And then restore the heathen ways. Green will remind you of the spring, Though this great day denies the thing. And mortifies the earth and all But your wild revels, and loose hall. Could you wear flowers, and roses strow Blushing upon your breasts’ warm snow, That very dress your lightness will Rebuke, and wither at the ill.

The brightness of this day we owe Not unto music, masque, nor show: Nor gallant furniture, nor plate; But to the manger’s mean estate. His life while here, as well as birth, Was but a check to pomp and mirth; And all man’s greatness you may see Condemned by His humility.

Then leave your open house and noise, To welcome Him with holy joys, And the poor shepherd’s watchfulness: Whom light and hymns from heaven did bless. What you abound with, cast abroad To those that want, and ease your load. Who empties thus, will bring more in; But riot is both loss and sin. Dress finely what comes not in sight, And then you keep your Christmas right.